Valve-operating mechanism



Dec. 27, 1927. 1,654,366

A. H. R. FEDDEN ET AL VALVE OPERATINGKECHANISM Filed Jan. 14. 1926 2 Sheets-Sheet 1 Dec. 27,1927.

A.' HQR. FEDDEN ET AL VALVE OPERATING MECHANISM Filed Jan. 14, 19

2 Sheets-Sheet 2 Imwnlors @EE. Feddm gym/ Patented Dec; 27, 1927.

, UNITED STATES PATENT OFFICE.

ALFRED HUIEERT ROY FEDDEN AND LEONARD FREDERICK GEORGE BUTLER, OE BRISTOL, ENGLAND, ASSIGNORS TO THE BRISTOL AEROPLANE COMPANY LIMITED,

'01 GLOUCESTER, ENGLAND, A BRITISH COMPANY.

VALVE-OPERATIN MECHANISM.

This' invention is for improvements in or relating to valve-operating mechanism for internal-combustion engines, and has for its object to provide an improved construction of the same whereby it is possible to alter the timing of the valve for the purpose of varying the power developed by the engine. The desirability for such variation arises in the case of engines used on aircraft. The power developed by an internal-combustion engine diminishes with reduction in atinospherlc pressure due to the ascent of the aircraft to higher levels this falling-off in power can be delayed by arranging that the engine has a higher compression ratio than'is suitable for workin at ground level, and making the timing of t e valves adjustable so that when running at ground level the power developed by the engine can be reduced to such an ex- 2 tent, as not to overstress the engine, and then readjusting the timing at higher altitudes in order to get the full benefit of the high compression ratio and develop the maximum power of which the engine is capable.

This invention is applied to engines of the type in which the valve-operating mechanism comprises a cam-shaft driven through a train gearing which is of an epicyclic type; that is to say, a train of gearing inwhich two coaxial gear-wheels are coupled by another gear-wheel or -wheels which are not coaxial with them. The last-mentioned wheel or wheels may in the normal operation have a planetary movement, in which case the train is a true epicyclic gear, or

their axis of rotation may'be normally stationary, in'which case the train is of an epicyclic type although it is not in normal operation ancepicyclic gear.

According to this invention, there is provided in an internal-combustion engine, the combination with valve-operating mechanism which comprises a cam-member driven through an epicyclic type of gear-train whereof one of the elements is normally held stationary, of means for moving said element Whilst thegear is in operation, to permit adjustment of the timing of the valves to vary the power developed by the engine.

81,315, and in Great Britain January 19, 1925.

This invention also covers the application of the said adjustment'to the valve-operating mechanism described in the specification of British Patent No. 180,436 the adjusting movement being imparted to the normally-stationary internally-toothed rack as mentioned in that specification.

In the accompanying drawings Figure 1 is a sectional elevation showing the crank-shaft of an internal-combustion engine and gearing whereby the valveoperating cams are driven, with the present invention applied to such gearing; Figure 2 is an end View of Figure 1 partly in section;

Figure 3 is a plan of Figure 2;

Figure 4 is an end View partly in section showing a detail of a modified construction;

Figure 5 is a plan of Figure 4;

Figure 6 is a longitudinal sectionof the parts shown in Figure 4:.

Like reference characters indicate like parts throughout the drawings.

In the arrangementillustrated in Figures lto 6, this invention is shown as applied to a valve-operating mechanism of the type described in the specification of British Patent No. 180,436.

Referring to Figures 1 to 3, the rotatable crank-shaft of the engine is indicated. at 10,'and the stationary crank-case at 11. An eccentric 12 is keyed on the crank-shaft to rotate therewith, and it carries rotatably mounted 'upon it a sleeve 13 carrying a spurgear 14 at one end and an internally-toothed wheel 15' at the other end. The internallytoothed wheel .15 meshes with a wheel 16 which is rotatable on the crank-shaft 10 but which is bolted to a drum or casing'17;-the operating-cams for-the inletand exhaustvalves of the engine are formed on the outer periphery of thisdrum 17 as indicated at 18.

The spur-gear l4 aforesaid meshes with an internally-toothed rack 19, and, as described in our prior specification aforesaid, this rack 05 19 was stationary, being secured on the crank-case'll.

The feature of the present invention is that rack 19 is adjustable, being made L this angular relationship becomes modified.

In practice, as applied to an aero-engine, the cam is retarded to give a late closing of the inlet-valve when the engine is running at ound'level. As the aircraft rises to higher altitudes, the setting of the cam relatively to the crank-shaft is advanced, so as to advance .the closing of the inlet-valve until, with maximum advance, the full compression who of the engine is made available and the maximum power is thereby developed. In practice it is possible to retard the inlet cam to such an amount that the engine develops say about 80% .of what would be its normal. full power when at ground level, and then at an altitude of say, 6,000 feet, when the full compression ratio can be utilized, the same power can be developed; in other words, there is no falling-oil 'in power due to the increasedaltitude of the engine, and the power which is developed is the maximum for which the engine is designed.

The means for efiecting the angular ads justment of the gear 19 is shown most clearly in Figure 2. The gear 19 is mountediin a bearing 31 (see Figure 1) on the crank-case, and its outer periphery is formed at oppo-' site ends of a diameter with two setsof worm-wheel teeth 20, two such sets being provided in order to balance the forces acting on the gearand to secure ease of adjustment. The bearing 31 is interru ted to accommodate these teeth. These teet '20 are engaged by worms 21 mounted on shafts 22, 23 which are rotatable in suitable bearings 24 on the crank-case of'the engine. The

. angular movement of the worms 21 is effected byrotating their shafts 22, 23, and for this, purpose the shafts are provided with arms 25', 26 respectively which are coupled by a tie-rod 27. The arms 25, 26 areso disposed relatively to one another that .the shafts 22, 23, are rotated in the appropriate direction for their "worms to impart rotation to the gear 19.

The shaft 23 carries a secondarm 28 coupled by a link 29 to a lever 30 which isin turn coupled by any convenient means to an operating. lever in the ilots cock-pit of the aircraft. Movement ,0 the pilots lever rocks the lever 30 and this movement is transmitted through the. link 29 to the shafts 23, 22 sothat the adjustment ofthegear 19 can be easily effected. even whilstthe engine-is running.

Figures 4, 5and .6 illustrate a slightly modified construction. Instead ofusing a worm-gear to effect the rotation of the gear 19, it is provided at one point on its eriphery with a radially-extending brac et 32 which is engaged by'a pin 33 carried on an arm 34 on a spindle 35. This spindle is capable of a slight rotational movement in its bearing 36 on the crank-case 11, and the parts are so disposed thatthis rotation of the spindle imparts the desired small rotatory movement to the. gear 19. The spindle is con'nected'in any convenient manner, as for example, by the lever 37 fast on it to the pilots control-lever.

Adjustable stops may be provided to limit the angular movement of the gear 19, and these are conveniently constituted by'bolts 38 mounted in the crank-case or a part carried thereby, as shown in Figure 4, thesebolts engaging the bracket 32. aforesaid or some other convenient partvcarried by the gear 19. In order to facilitate theadjustment of the gear it is preferred to make the bush 36 eccentric, that is to say, its outer periphery is cylindrical, and is eccentric from the bore which receives the spindle 35. With this construction the position of the gear-wheel; can be adjusted in the initial timing of the.

engine, and then the bush 36 and spindle 35 can be set in the most convenient angular relationship to enable the pin 33 to impartv 36 has been a place and the adjusting control isefiected by rotation of the spindle 35 in it.

' What we claim as our desire to secure by Letters Patent isz- 1. An engine .crank case for accommodating epicyclic valve operating gearing having adjustable advancing and retarding means, having an the crank aft of the engine is adapted to pass, s'aidcrank.case having afportion overanging the crank shaft -when in position glpening in one end through which the desired adjusting movement to the gear 19, it being appreciated that when the bush justed it has been locked in;

invention and and spaced thereabout, and a support mounted on said portion overhanging the crankshaft for accommodating an epicyclic valve operating earing on the crank shaft, and means on t e crank case for sup citing the adjustable advancing and retar mg means. of said gearing.

2. An engine crank case for accommodating. a crank shaft and an e' icyclic valve 0 crating gearing. on the sha and provide 7 with ad uStable means for advancing and retard--- shaft and dlsposed in position to rovide a space between the support and t e crank 6 ing the gearing, having a 'rtion adapted crank shaft,- said support arranged in line to enclose a crank shaft an provided with with and adapted to support the adjustable 10 means for mounting the adjustable advancelement of sald gearing. ing and retarding means, and a support In testimony whereof we have signed our 5 mounted on the crank case adapted to ennames to this specification;

vcircle the crank shaft and spaced therefrom e support the ALFRED HUBERT ROY HIDDEN.

for accommodating within th epicyclic valve operating gearing on the RD FREDERICK GEORGE BUTLER. 

